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Grass Hay Production as Influenced by N‐P Topdressing and by Residual P 1
Author(s) -
Ludwick A. E.,
Rumburg C. B.
Publication year - 1976
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1976.00021962006800060022x
Subject(s) - dactylis glomerata , bromus inermis , phleum , agronomy , hay , loam , fertilizer , poa pratensis , red clover , nutrient , growing season , festuca pratensis , forage , grazing , zoology , poaceae , biology , soil water , lolium perenne , ecology
Information is limited on the response of grass to top dressing N‐P combinations on soils deficient in both nutrients, especially concerning time of application. The purpose of this study was to compare fall and spring topdressing of N‐P combinations for grass hay production and to evaluate residual P during succeeding seasons. A 4‐year experiment was conducted on a Fola cobbly sandy clay loam soil (Borollic Camorthid) near Gunnison, Colorado. Vegetation consisted of a mixed stand of bromegrass ( Bromus inermis Leyss.), timothy ( Phleum pratensis L.), orchardgrass ( Dactylis glomerata L.), bluegrass ( Poa pratense L.), and occasional plants of red clover ( Trifolium pratense L.). Treatments were 4 rates of both N and P applied either in the fall or spring, prior to the first growing season. Residual P was evaluated the following three seasons. Hay yields the 1st year (1972) were significantly increased from 2.51 metric tons/ha with no fertilizer to 10.77 for the highest fertilizer combination of 358 and 59 kg/ha of N and P fall applied. Yields increased with increasing rates of both nutrients. Yields from fall applied N‐P combinations averaged 1.0 to 2.5 metric tons/ha greater than yields from similar treatments spring applied. Apparently the additional time and opportunity for dissolution of the P granules and movement through the thatch and into the surface soil resulted in the fall treatments being superior to similar treatments spring applied. Uptake of both N and P followed trends similar to yields. Yields in 1973 and 1974 were increased over the control (O‐P) by the initial P treatments, although yields and P uptake declined each year. Time of initial fertilizer application (fall vs. spring) did not significantly affect yields nor P uptake beyond the first season. Although residual P continued to increase yields and P uptake in 1975 (significant over the control at the highest P rate), reapplying P significantly increased both over all residual P levels. Bicarbonate extractable soil P levels were markedly increased in the upper 2.5 cm of soil by P topdressing. There was no evidence of P movement below 5.0 cm.